polymyositis

poly·myo·si·tis

noun \-ˌmī-ə-ˈsīt-əs\

Definition of POLYMYOSITIS

: inflammation of several muscles at once; specifically : an inflammatory disease of unknown cause that affects muscles and especially skeletal muscles, is characterized typically by weakness usually of the proximal muscles (as of the pectoral or pelvic girdles or of the neck), muscle and joint pain, pathological muscle changes (as fiber degeneration or infiltration by lymphocytes), pneumonia, and cardiac abnormalities (as arrhythmia or myocarditis)—see dermatomyositis